Bideauxite

Chemical formula: Ag<sup>1+</sup>Pb<sup>2+</sup><sub>2</sub>F<sub>2</sub>Cl<sub>3</sub>

Bideauxite is a rare lead and silver halide, forming colorless or white, isometric crystals with an adamantine luster.

## Characteristics Bideauxite is a rare mineral from the halide group, chemically classified as a lead and silver fluoride and chloride. It occurs as small, well-formed, isometric crystals, most often in the form of cubes or octahedra. Crystals are usually colorless to white, sometimes with a yellowish tint. Their strong, almost adamantine luster is characteristic, distinguishing them from the host rock. ## Physical Properties This mineral is relatively soft, with a hardness of about 3 on the Mohs scale. It is very dense, which is typical for lead-bearing minerals; its density is approximately 6.27 g/cm³. Crystals are transparent to translucent. It exhibits perfect cleavage in three directions, parallel to the cube faces. ## Colors and Varieties Bideauxite is usually colorless or white. Some specimens may acquire a pale yellow hue. No named varieties of this mineral are recognized. ## History and Name The mineral was discovered in the Tiger mine in Pinal County, Arizona, USA. It was described in 1970 by Sidney A. Williams. The name "bideauxite" honors Richard A. Bideaux (1935–2004), an American mineralogist and collector, who co-authored the "Handbook of Mineralogy" and made significant contributions to the mineralogy of Arizona. ## Uses Bideauxite has no industrial applications. It is a purely collector's mineral, sought after for its rarity, attractive crystals, and origin from a classic locality.

Properties

Mohs hardness
3
Luster
Adamantine
Streak
White
Density
6.27
Cleavage
Perfect on {100}
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Cubic

Diagnostic features

## Identification Key diagnostic features of bideauxite include its regular (isometric) crystal habit (cubes, octahedra), very high density, strong, adamantine luster, and occurrence in the oxidation zones of lead deposits. Perfect cubic cleavage is also characteristic, although difficult to observe in small crystals. ## Distinguishing from Similar Minerals Bideauxite can be confused with other colorless or white halides from oxidation zones, such as cerussite or anglesite, but it differs from them in crystal habit and significantly stronger luster. It is distinguished from halite (rock salt) by its much higher density and luster. Chemical tests confirming the presence of lead, silver, and chlorine are the definitive method of identification. ## Crystal Forms Bideauxite crystallizes in the isometric system, most often forming small but well-developed cubes, less commonly octahedra and rhombic dodecahedra. Crystals occur as single forms grown on the host rock or in small druses.

Geological environment

## Genesis Bideauxite is a secondary mineral, forming in the oxidation zones (so-called iron caps) of hydrothermal lead and silver ore deposits. It forms under arid conditions, as a result of the reaction of chlorine- and fluorine-rich solutions with primary ore minerals, such as galena. ## Mineral Associations This mineral often co-occurs with other rare secondary minerals of the oxidation zone. At its type locality (Tiger mine), it was found in association with anglesite, boleite, cerussite, leadhillite, matlockite, phosgenite, and wulfenite. ## Localities The most important and classic locality for bideauxite, from which the best-known specimens originate, is the Tiger mine in the Mammoth-St. Anthony District, Pinal County, Arizona, USA. This is its type locality. Additionally, its presence has been noted in small quantities at the Margarita mine in the Greek region of Lauríon (Lavrio).

Rarity

Very rare

For collectors

## Quality Criteria The most desirable bideauxite specimens are characterized by sharp, well-defined crystals with a strong, adamantine luster. Transparent, colorless cubes, contrastingly set on a rock matrix, are highly prized. Crystal size is a key factor – specimens with crystals exceeding a few millimeters are exceptionally rare and valuable. Aesthetic arrangement on the matrix and association with other rare minerals from the Tiger mine increase the specimen's value. ## Popular Localities The only source of specimens of collector's significance is the historic Tiger mine in Arizona. Specimens from this locality are considered classics and fetch high prices on the collector's market. Material from other localities is extremely rare and primarily of scientific interest.

Care and storage

## Cleaning Due to its softness and perfect cleavage, bideauxite requires very careful handling. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used to remove dust. Avoid contact with water and any chemicals. ## What to Avoid Avoid ultrasonic cleaners, chemical agents, acids, and sudden temperature changes. The mineral is soft and easily scratched. Due to its perfect cleavage, even a slight impact can cause the crystal to crack or break apart. ## Storage Bideauxite specimens should be stored separately in a padded box to prevent abrasions and mechanical damage. They should be protected from dust and moisture. It is not sensitive to light.

Sources

Read more